A rider is necessarily required to wear a helmet when riding a two-wheeled vehicle such as a motorcycle, and the helmet generally has a front opening at a front side of its main body in order to allow a wearer to obtain a front view. Further, the helmet generally has a selectively retractable shield to prevent wind or dust from being introduced through the front opening while the motorcycle moves forwards.
For this reason, the helmet includes a certain coupling unit for coupling the shield to the helmet main body. To be more specific, the coupling unit includes shield coupling assemblies provided at both sides of the helmet main body and assembly coupling parts provided at both inner ends of the shield so as to be fitted and coupled to the shield coupling assemblies.
A helmet has a hermetically sealed structure where little air can get in or get out, which makes a helmet wearer easily feel it is stuffy inside the helmet or which makes the inside of a shield damp with humidity, thereby blocking the helmet wearer's view. In order to solve these problems, conventionally, a shield which may block a wearer's view is opened or air outside a helmet is introduced into the helmet through a separate ventilation opening. Further, there has been known a helmet which, if it is provided with an openable shield, includes a separate shield locking device for preventing unintended opening of the shield.